As a two-shaft gas turbine power generating facility, there is, for example, a facility described in the following Patent Document 1. The two-shaft gas turbine power generating facility includes a two-shaft gas turbine, a power generator, a starting motor, a secondary battery, a first frequency converter that controls power transmission/reception between the starting motor and a power system, and a second frequency converter that controls charging and discharging of power between the secondary battery and the power system.
The two-shaft gas turbine includes a compressor that compresses air to generate compressed air, a combustor that generates combustion gas by combusting fuel in the compressed air, a high-pressure turbine that is driven by combustion gas, and a low-pressure turbine that is driven by exhaust gas discharged from the high-pressure turbine. A rotor of the high-pressure turbine, the compressor rotor, and a rotor of the starting motor are mechanically connected to one another. Also, the rotor of the low-pressure turbine and the rotor of the power generator are mechanically connected to each other. However, the rotor of the high-pressure turbine and the rotor of the low-pressure turbine are not mechanically connected.
Even if the output of the power generator is increased by increasing a flow rate of the fuel to be supplied to the combustor when the required output for the two-shaft gas turbine power generating facility rapidly increases, the output of the power generator may not conform to the rapid increase in the required output. Therefore, as described in Patent Document 1, technology for temporarily employing the starting motor as a power generator to compensate for insufficiency in an output of the power generator with respect to the required output with an output from the starting motor using the power generated by the starting motor has been proposed.
The output energy of the starting motor is the rotational inertia energy of the high-pressure turbine rotor and the compressor rotor. Thus, a time required to take out the output from the starting motor is a time of about several seconds that is a significantly short time. Consequently, when the required output for the two-shaft gas turbine power generating facility rapidly increases, insufficiency in an output of the power generator for the required output may not be compensated for with the output from the starting motor using only an output based on the above-mentioned rotational inertial energy. Therefore, in the technology described in Patent Document 1, discharging of power from a secondary battery to a power system is proposed in this case.